1. Field of the Invention
This invention relates to a cathode ray tube employed in a system used for displaying video data such as a television receiver and a degaussing coil used in the tube. More particularly it relates to a cathode ray tube in which the degaussing coil is attached to the outer periphery of a funnel of the tube and is fed with an alternating current for degaussing the magnetic components provided outside and inside of the main body of the tube such as the aperture grill or frame.
2. Description of Prior Art
In a cathode ray tube, an aperture grill or a frame of a magnetic material, arranged on the inner and outer sides of the main tube body, tend to be magnetized under the influence of terrestrial magnetism. If the aperture grill or frame is magnetized, the three beams of R, G and B radiated from the electron guns cannot be converged each at a point on a phosphor screen, as a result of which the displayed picture suffers from color deviations or distortions.
For preventing such failure in convergence caused by terrestrial magnetism, a cathode ray tube is employed in which a degaussing coil is mounted on the outer side of a funnel for degaussing the magnetic components arranged on the inner and outer sides of the main tube body.
FIG.1 shows an illustrative arrangement of this type of cathode ray tube.
The cathode ray tube shown in FIG. 1 includes degaussing coils 103, 104 attached on the outer periphery of a funnel 102 of a main tube body 101. These degaussing coils 103, 104 are connected to a degaussing circuit, not shown, from which the coils are fed with alternating current which is decreased with lapse of time for degaussing the main tube body 101.
The degaussing coils 103, 104, used for the cathode ray tube, each consist in a copper wire bent into a ring and subsequently wrapped in its entirety with an electrically insulating tape, known as a UL tape, formed of an electrically insulating material, such as polyvinyl chloride, by way of an operation known as forming, so that it has a circular cross-sectional shape.
Since the conventional degaussing coil is circular in cross-section, it is partially protruded from the outer surface of the cathode ray tube, when attached thereto, thereby increasing the outer size of the cathode ray tube.
Besides, since the forming is achieved by simply wrapping the UL tape around the copper wire, a problem is raised in operability that the coil tends to be deformed during transport so that it becomes necessary to perform re-forming prior to attachment to the cathode ray tube.